This invention relates to an air bag of an air bag device for use in a vehicle as an occupant protection device.
An air bag device is a device which protects an occupant in the event of a vehicle collision by inflating an air bag, and comprises an inflator, which is a gas generator, and an air bag capable of inflation with gas from the inflator, installed, for example, in an instrument panel or in a central part of a steering wheel of a vehicle.
An air bag is made by stitching together peripheral parts of a plurality of panels made of flexible cloth or the like.
As the panels forming the air bag, so-called non-coated woven fabrics not coated with rubber or resin have been used, but when a non-coated woven fabric is cut by die cutting or knife cutting, at the cut ends, where the cut is almost parallel with a weave thread direction, there has been a tendency for warp or weft constituting the woven fabric to easily detach from the weave structure, i.e., for thread fraying to easily occur.
Because the cut ends are disposed inside the air bag, thread fraying has occurred due to viscous drag of gas flow produced by the inflator on inflation.
Conventionally, to prevent the thread fraying from occurring, as shown in FIG. 6, in an air bag 100 for a driver's seat, around the entire periphery of an occupant-associated panel 101 disposed on an occupant side and of an inflator-associated panel 102 disposed on an inflator side, the seam allowance (the distance from the seam 103 to the cut end) L has been made large (for example 20 mm or more). However, when the seam allowance L is made large around the entire periphery like this, the mass of the air bag becomes large and its bulk when folded also increases.
Also, conventionally, in cutting a non-coated woven fabric, thread fraying has sometimes been prevented by using laser cutting or the like and fusing the cut ends of the fabric. However, the use of a laser or the like leads to increased cost in productivity and equipment aspects.